Defending Aquinas’ Theistic Proofs from Kant’s Antinomies, Part 1

When German philosopher Immanuel Kant attempted to retrieve reason from the clutches of Hume’s skepticism, he limited knowledge and gutted metaphysics. Kant did this in part through a series of antinomies of paradoxical conclusions to show that understanding beyond the sensible world leads to an antinomy. Kant believed that by sacrificing metaphysical knowledge he saved knowledge of the sensible world from skepticism. If Kant’s antinomies are logically sound, repercussions for metaphysical claims, like St. Thomas Aquinas’ theistic proofs, are devastating. However, it is my intention to show weaknesses in Kant’s critique of reason and that Aquinas’ theistic proofs, placed in the metaphysical realm of natural law, is sound.

Natural and Eternal Law

According to Aquinas, philosophy can prove and clarify by means of human reason certain a priori truths. He believes that as intelligent beings, we are capable of understanding the world by our cognitive powers. He recognizes the limitations of human reasoning and separates laws into different categories. Eternal law is unchanging and known to humans through its reflection on our minds and is revealed in part through human and natural law. The category of law that is in primary view for this post is natural law, which is general and deals with what is necessary and logical. While Aquinas primarily speaks of the categories of laws in terms of ethics, the natural law applies also to the way in which we apprehend truths of the world.

There are universal truths, things that are said to be a priori, yet our knowledge of them starts with the senses, which we use to learn universal truths by reasoning backwards. By examining triangles, I can learn it is a universal truth that triangles are three-sided closed shapes. Universal truths are not relegated to geometry alone, but it is an example of how humans are able to examine the world to reach a fuller understanding of it. This is also seen in St. Thomas’ five theistic proofs.

Five Theistic Proofs

1. Argument from motion starts with the senses. Humans know through experience that things move and that nothing can move itself. Since everything is moved by something else, reason shows that there would be a primary mover. If not, nothing would move.
2. In his argument from efficient cause, Aquinas relied on the Aristotelian understanding of a primary source that pushes something into existence. Efficient cause is the primary source of change, like the knowledge a carpenter has when creating a table. Just like a table is unable to be its own cause, the world came into existence through a primary efficient cause.
3. In the argument from possibility and necessity, we recognize through sensory experience that there are things in nature that are possible to not exist. In other words, it is not necessary for certain things to exist, and in fact some species have ceased to exist. Since there was a time when each contingent thing did not exist, there could be a time when nothing existed. If nothing existed, then nothing could have been brought into existence. Since this is not possible, there must be a being of necessity that does not rely on any other for its existence but instead is the cause of all other beings.
4. The argument from gradation of being states that some things are better or worse than others and whatever is the maximum of a genus is the cause of what all others are compared to. Therefore, there must be a perfection of goodness that is the cause of all other good things.
5. The argument from design examines the world and shows that natural bodies work toward some goal, even the natural things that lack knowledge. For example, planets revolve around the sun. The late Stephen Hawking wrote, “The latest advances in cosmology explain why the laws of the universe seem tailor-made for humans.” While Hawking denies a creator, Aquinas would use logic to respond that because natural things are directed toward a goal, and that goal being for the existence of humans, there must be an intelligent being directing all things to their end.

Kant attacks these proofs in The Critique of Pure Reason in several ways, but I will focus on his antinomies in Wednesday’s blog post.